The synthesis of isotopically labelled glucoraphanin for metabolic studies

The first synthesis of a stable isotopically labelled derivative of the glucosinolate glucoraphanin, namely [10-¹³C,11,12-²H₅]glucoraphanin, is described. This also represents the first total chemical synthesis of glucoraphanin itself.     

Unique selectivity windows using selective displacers/eluents and mobile phase modifiers on hydroxyapatite

A detailed study was carried out to combine the unique selectivity of ceramic hydroxyapatite (CHA) with the separation power of selective displacement chromatography. A robotic liquid handling system was employed to carry out a parallel batch screen on a displacer library made up of analogous compounds. By incorporating positively charged, metal chelating and/or hydrogen bonding groups into the design of the displacer, specific interaction sites on CHA were targeted, thus augmenting the selectivity of the separation. The effect of different mobile phase modifiers, such as phosphate, sulfate, lactate and borate, were also investigated. Important functional group moieties and trends for the design of CHA displacers were established. Selective batch separations were achieved between multiple protein pairs which were unable to be resolved using linear gradient techniques, demonstrating the applicability of this technique to multiple protein systems. The specific interaction moieties used on the selective displacer were found to dictate which protein was selectively displaced in the separation, a degree of control not possible using a mono-interaction type resin in displacement chromatography. Mobile phase modifiers were also shown to play a crucial role, augmenting the selectivity of a displacer in a synergistic fashion. Column separations were carried out using selective displacers and mobile phase modifiers identified in the batch experiments, and baseline separation of the previously unresolved protein pairs was achieved. Further, the elution order in these systems was able to be reversed while still maintaining baseline separations. This work establishes a new class of separations which combine the selectivities of multi-modal resins, displacers/eluents, and mobile phase modifiers to create unique selectivity windows unattainable using traditional modes of operation.     

Cyclotomic Integers,Fusion Categories,and Subfactors

Dimensions of objects in fusion categories are cyclotomic integers, hence number theoretic results have implications in the study of fusion categories and finite depth subfactors. We give two such applications. The first application is determining a complete list of numbers in the interval (2, 76/33) which can occur as the Frobenius-Perron dimension of an object in a fusion category. The smallest number on this list is realized in a new fusion category which is constructed in the Appendix written by V. Ostrik, while the others are all realized by known examples. The second application proves that in any family of graphs obtained by adding a 2-valent tree to a fixed graph, either only finitely many graphs are principal graphs of subfactors or the family consists of the A _n or D _n Dynkin diagrams. This result is effective, and we apply it to several families arising in the classification of subfactors of index less than 5.     

Compaction and tensile forces determine the accuracy of folding landscape parameters from single molecule pulling experiments

We establish a framework for assessing whether the transition state location of a biopolymer, which can be inferred from single molecule pulling experiments, corresponds to the ensemble of structures that have equal probability of reaching either the folded or unfolded states (P(fold)=0.5). Using results for the forced unfolding of a RNA hairpin, an exactly soluble model, and an analytic theory, we show that P(fold) is solely determined by s, an experimentally measurable molecular tensegrity parameter, which is a ratio of the tensile force and a compaction force that stabilizes the folded state. Applications to folding landscapes of DNA hairpins and a leucine zipper with two barriers provide a structural interpretation of single molecule experimental data. Our theory can be used to assess whether molecular extension is a good reaction coordinate using measured free energy profiles.     

Acid-induced dimerisation of 1,2-di(thien-2-yl)ethanone

Treatment of 1,2-di(thien-2-yl)ethanone with aqueous 75% (v/v) sulfuric acid gives a dimer in which the units are linked head-to-head via a thiophene-tetrahydrothiophene bond.     

On the singularity of Green's tensor for a perfectly conducting semi-infinite cone

This paper is intended to clarify a misunderstanding concerningthe source singularity of the electric Green's tensor for aperfectly conducting semi-infinite cone of circular cross-section.Tai's series expansion of the Green's tensor is known to lacka singular term at the source region. Jones has reconstructedthe solution to this problem and has pointed out the differencebetween his result and that of Tai. The aim of our paper isto demonstrate that, although Jones's closed-form solution iscorrect, there is a mistake in his comparison with Tai's seriessolution. We conclude that one of the two additional singularterms that Jones claims as missing from Tai's formula must beomitted. Besides, we compare Jones's closed-form solution withSmyshlyaev's solution to the very same problem. We concludethat the magnetic field expressions given by Jones and Smyshlyaevcoincide, but a singular term is missing from Smyshlyaev's expressionfor the electric field.     

A study of shear-stress relaxation anomalies in binary mixtures of monodisperse polystyrenes

We report measurements of the nonlinear relaxation moduli after a step-shear strain of polystyrene solutions with nearly monodisperse and with bidisperse distributions of molecular weight. We find, as have others, that for monodisperse solutions with M/M_e > 60, there are anomalies, such as an unusually low nonlinear modulus and a kink in a plot of shear stress versus time after the step strain. Here M is the polymer molecular weight and M_e is the entanglement molecular weight. We find that in the bidisperse solutions the anomalies persist as long as M_w/M_e > 60, where M_w is the weight-averaged molecular weight of the bidisperse solution. The persistence of the anomalies in bidisperse solutions disagrees with a theory of Marrucci and Grizzuti that attributes the anomalies to strain inhomogeneities similar to shear banding. The Marrucci-Grizzuti theory predicts that as little as 10% short chains in the bidisperse mix should eliminate the anomalies, whereas in the experiments reported here at least 30% is required. Nevertheless the way in which the anomalies disappear at high strains when one increases the fraction of low-molecular-weight component is qualitatively similar to the theoretical predictions and supports the notion that strain inhomogeneities occur in these systems. © 1992 John Wiley & Sons, Inc.     

Observation ofD S ** (2536) meson production by neutrinos in BEBC

Zeitschrift für Physik C Particles and Fields - Neutrino interactions in BEBC produce theD ** (2536) charmed strange meson. The mass of this state is 2534.2±1.2 MeV. The production rate...     

Determination of the ratior v =d v u v of the valence quark distributions in the proton from neutrino and antineutrino reactions on hydrogen and deuterium

Zeitschrift für Physik C Particles and Fields - A set of proton longitudinal polarized distributions, worked out under the assumption of small gluon polarization, is used to evaluate several...     

Slopes of effective divisors on the moduli space of stable curves

Research partially supported by NSF Grant #DMS-84-02209.